Typically, a solid oxide fuel cell (SOFC) employs an electrolyte of ion-conductive oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, normally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the fuel cell stack, it is required to apply a stacking load for tightening the fuel cells in the stacking direction. In order to maintain the desired sealing performance, the required stacking load is high in portions where reactant gases (in particular, the fuel gas) flow in the fuel cell stack. Further, in order to prevent the MEAs from being damaged undesirably, a relatively small load needs to be applied to portions where the MEAs of the fuel cell stack are supported. For this reason, the load applying mechanism for applying the stacking load to the fuel cell stack is required to apply different loads to the portions where gas sealing is performed and the portions where the MEAs are supported.
In this regard, for example, in a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2007-073359, as shown in FIG. 10, in a fuel cell formed by stacking power generation cells 1a and separators 2a, a tightening load is applied to the fuel cell using tie-rods 3a and nuts 4a to maintain the desired gas sealing performance. A weight 5a is disposed on the power generation cells 1a, above the center of the separators 2a. Power generation elements of the power generation cells 1a tightly contact each other by the load applied by the weight 5a. 
Further, as shown in FIG. 11, a solid polymer electrolyte fuel cell disclosed in Japanese Laid-Open Patent Publication No. 08-088018 includes a fuel cell stack body 1b formed by stacking unit cells through electrically conductive separators, and tightening means for tightening the fuel cell stack body 1b in the stacking direction. The tightening means includes first tightening means 2b for tightening an area where manifolds are provided, and second tightening means 3b for tightening an area where power generation is performed. The first tightening means 2b includes bolts 4b, and the second tightening means 3b includes bolts 5b. 
Further, in a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2006-179402, as shown in FIG. 12, a stack body formed by stacking a plurality of unit cells 1c is sandwiched between a pair of end plates 2c, 3c. A load is applied to portions of the unit cells 1c where sealing is required by applying a tightening load to components between the end plates 2c, 3c using a plurality of through bolts 4c and nuts 5c. 
A load adjuster 6c adjusts a pressure force of a spring box 7c applied to an end plate 3c. By the pressure force of the spring box 7c, a tightening load is applied to the power generation area of the unit cell 1c. 